Various attempts have been made to shield a telephone subscriber's number from unwanted calls (e.g., telemarketer calls). Having an unlisted telephone number provides some protection from unsolicited calls from the public at large. However, unlisted numbers provide little protection from telemarketers because computer controlled sequential dialing of multiple numbers is commonly performed by telemarketers with the express intent of reaching both listed and unlisted telephone service subscribers.
Some telecommunications systems (e.g., the public switched telephone network (PSTN)) use Signaling System 7 (SS7) standards for communication of telephone calls. SS7 is a digital communications protocol that supports various messaging and call information features that facilitate a variety of telephone services. SS7 facilitates advanced intelligent network (AIN) call processing, such as call handling instructions obtained by a switch from a service control point (SCP). The SCP may include logic (e.g., call processing records) used to provide a switch with specific call processing instructions based on information obtained from a database and/or call information provided by the switch or another source.
Some telecommunications systems use Voice over Internet Protocol (VoIP) based networks for communication of telephone calls. VoIP is a set of facilities used to manage the delivery of voice information over a data network, such as the Internet. VoIP involves sending voice information in digital form in discrete packets rather than by using traditional circuit-committed protocols of the PSTN.
As telecommunications companies begin to deploy large-scale VoIP networks, they are looking for voice applications that will differentiate them from other VoIP service providers. For example, VoIP service providers have been attempting to recreate some existing PSTN-based features on their VoIP-based products. However, some enhanced PSTN-based features remain unavailable in VoIP networks. Call intercept (or call screening) is one feature currently unavailable in VoIP networks. PSTN-based call intercept is built on the AIN platform, and allows a subscriber to screen incoming calls from unknown parties and to redirect the call without ever talking to a calling party.